This invention relates to spirometers, and more particularly, to the class of spirometers which employs turbine operation to develop a representation of air volume exiting the lungs of a patient.
Spirometers involve interesting design problems and limitations, in that a high degree of clinical safety and operational accuracy is required, while structural simplicity, cost efficiency, and ease of sterilizability are also highly desirable. Yet these general goals are often conflicting, in that accuracy of measurement often leads to complications of design which are detrimental to reliability. Heavy construction, while promoting reliability leads to serious problems of high friction and lack of response to low flows and/or to high inertia which promotes "coasting" after high flows. In addition, use of readily available materials in conventional design usually involves structural aspects not readily amenable to sterilization techniques and general convenience of clinical use. The present invention is accordingly directed to provision of a spirometer which is accurate, relatively inexpensive, compact and convenient for clinical use, structurally amenable to sterilization, and reliable and durable under clinical conditions.